Posted on: March 2, 2017 at 1:45 pm
Last updated: November 20, 2020 at 11:52 am

Seafood 101 – Fish Toxicity Levels from Lowest to Highest

With so many scares about mercury, farmed fish, radiation leakage, and parasites, it’s not easy to know whether you’re eating toxic fish or a non-toxic one. You’d buy organic produce and meats, but do you get a little confused when you go to pick up fish?


From not knowing the fish toxicity levels to being confused about the labels, buying fish can feel like a task you want to avoid. However, fish can be so beneficial for our bodies and our brains with their protein and omega-3s.

Here’s your how-to guide for avoiding toxic fish and getting the good stuff. And you’ll never have to be confused at the supermarket again!



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Pro: Tuna is widely available and tastes great in just about anything. It contains protein, omega-3s, and even selenium, which can help prevent mercury contamination.

Con: Tuna such as albacore have moderate mercury levels, so it’s not generally considered safe to consume excessively. Limit yourself to only a few ounces of tuna per week.

Best Kind to Buy: Canned light tuna is the best kind to buy. (BPA-free can? Bonus!)



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Pro: Salmon is loaded with Vitamin D, B vitamins, omega-3s, protein, and antioxidants.

Con: Most salmon still contain trace amounts of mercury, so consuming this fish in excess isn’t a good idea.

Best Kind to Buy: Wild-caught salmon is best as it’s the highest in omega-3s and nutrients!

Predatory Fish

Pro: It’s unlikely you’d see these fish at the supermarket, so the chances you’ll buy them are less.

Con: Shark, swordfish, and king mackerel are all predators, and predatory fish are bad because they generally contain high amounts of mercury.

Best Kind to Buy: Avoid these fish if you can.


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Pro: Crab tends to be pretty low in mercury [1].

Con: Bottom feeders, so should not eat the guts (like you would do that). Crabs should ideally be cooked the same day they’re purchased [2].

Best Kind to Buy: The fresh kind!


Pro: Shrimp are also low in mercury; therefore, they tend to be safer to eat during pregnancy [3].

Con: Many shrimp are now being farmed, which is something you’ll want to avoid.

Best Kind to Buy: Wild-caught shrimp!

Sardines and Anchovies

Pro: These small fish are low in toxins and provide lots of omega 3s and vitamin D. Anchovies are also rich in iron + omega 3s.

Con: Not everyone likes these fish.

Best Kind to Buy: Fresh or canned is fine.


Pro: Shellfish such as oysters contain high levels of trace minerals like phosphorus, selenium, manganese, copper, and iron.

Con: Shellfish are often more contaminated, but clams are the least contaminated. Oysters and lobster should be eaten occasionally. Scallops have the least amount of mercury compared to oysters, tuna, and even crab [4]. Mussels contain low amounts of mercury as well [5].

Best Kind to Buy: Shellfish that have been allowed to grow in their natural environment are best, but try to avoid kinds from China.

Rules of Thumb

The following general rules to fish toxicity can help when you’re in the supermarket trying to find ones that won’t poison you or your family.

Fish from remote bodies of water are better. Think the Atlantic ocean and Alaska. Avoid lakes, rivers, and freshwater fish from polluted areas.

Choose fast-growing fish. Fish such as mahi-mahi and tilapia are better than slow growing fish, as they have less time to be exposed to toxins.

Fish from China is best avoided. The waters around China are generally heavily polluted, so you tend to get a lot of toxic fish from those waters. Unfortunately, most seafood from Costco and Sam’s Club is from China unless otherwise noted on the packaging.

A note on Pacific fish. Since Fukushima, there has been a lot of concern about radiation contamination in seafood found in the Pacific ocean. While today, the levels are generally considered low, you can read more about what scientists know here.

A word on farmed fish. Farmed fish are usually just as bad as animals on a factory farm and contain antibiotics, growth hormones, and are fed GMOs like corn and soy, and even dyes. Eek! Have half the omega-3 content. If you do choose farmed fish, U.S-raised are better than Asian. Watch out for these breeds that are typically farmed—salmon, trout, tilapia, and shrimp.

It shouldn’t have to be a hassle to find fresh foods that will nourish our bodies. When choosing fish, remember that farmed fish or fish from China should be at the bottom of your list. To avoid fish toxicity and do your part, try to choose fish that have lived in a natural environment and been sustainably caught. Keep in mind the regions that are the most polluted. And when eating freshwater fish, choose those that have been caught away from pollution.

Avoiding mercury can be difficult in itself, but by eating some great foods, you can detoxify. Want to know how to detoxify mercury? Selenium binds to mercury and neutralizes it in your body.

Jenn Ryan
Freelance Health & Wellness Writer
Jenn Ryan is a freelance writer and editor who's passionate about natural health, fitness, gluten-free, and animals. She loves running, reading, and playing with her four rescued rabbits.

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